Right but basically wrong: comments on Canales et al. 'A critical assessment of the consciousness by synchrony hypothesis'.

Abstract

The authors are right in holding the viewthat neural synchrony does not seem toprovide a solution for the ‘hard problem ofconsciousness’ (Chalmers 1996). They arealso right in that most of the evidencepresented for the role of neuralsynchronization in perceptual binding iscorrelative and not causal. They areessentially wrong in all their remainingpoints.It is true that neural synchrony does notsolve the hard problem, but then, nobodyhas proposed a solution for the hardproblem. It is not even clear that such aproblem exists or that a scientific solutioncan ever be given to the hard problem(Dennett 1991). Certainly it is premature tomake a definitive statement on this subjectat the present stage of research.By contrast, neural synchrony does seemto be at least part of the neural correlates ofconsciousness, which ask what are theminimal neural activities and structures thatare necessary and sufficient for a consciousact to take place (Crick & Koch, 1990). In arecent paper we have been able to showthat, long-range synchrony correlates withvisual awareness but local synchrony doesnot (Melloni et al. 2007). This result,suggests that synchronic activity inside arestricted cortical area remains unconsciousand that consciousness arises only when ‘allthe brain’ is informed via long-rangesynchronic interactions. It can behypothesized that this would be the basisfor the unified character of experientialconsciousness.The authors correctly point to thecorrelative nature of most of the evidencesupporting a role of neural synchrony bothin consciousness and in visual featurebinding. To our knowledge there is a singleexperiment showing the causal involvementof neural synchrony in an odordiscrimination task (Stopfer et al. 1997).However it must be stated that the sameholds true for all electrophysiology in allthe fields of neuroscience. From the studiesof Hubel and Wiesel on, essentially allelectrophysiology consists of manipulatingthe stimuli, recording the neural responseand proposing mechanisms based on thecorrelations found. The only alternativetheory for visual binding (the cardinal celltheory, Barlow 1972) is also mostly basedon correlative evidence with the onlyexception of a few works conducted byShadlen and collaborators (Huk & Shadlen2005)An argument is made against synchronyas a mechanism for consciousness becauseof the participation of synchrony in non-conscious (anesthetized) animals and inbrain areas not obviously related toperceptual consciousness (thehippocampus). Both arguments arelogically false. The fallacy is tantamount toclaiming that because